An automobile's turn signals (sometimes called “turn indicators” or “blinkers”) indicate the intention of a driver to turn or to change lanes. The turn signal's flash rate is generally constant, produced by a signal controller which sometimes comprises an oscillator prone to drift its frequency according to the automobile battery voltage. The oscillator triggers accordingly on/off a relay that switches power to the turn signal lights. Often the oscillator and the relay are implemented in the same unit called “signal flasher blinker relay.” Accordingly, the flash rates tend to be within the range of 60 and 120 flashes per minute.
To remind a driver that his/her turn signals are operating, so as not to forget to turn them off after changing lanes, the repetitive sound of the relay is made audible to the driver. This sound can be the natural mechanical noise of a relay that switches the current to the turn signal electronics.
A problem frequently arises when a driver listens to music while operating turn signals: the loud sound of the turn signal interferes with the enjoyment of listening to the music, and this interference tends to quickly annoy the driver. Unfortunately, this annoyance can motivate some drivers to consciously decide not to activate turn signals, which detracts from the driver's safety and the safety of those proximate the driver.
It would be desirable if the sound of the blinker relay would not interfere with the music while still notifying the driver that the turn signal is on and needs to be turned off.